1. Field of the Invention
The invention relates to a method of making a monolithic microwave integrated circuit (MMIC) with conductive members for integrated passive components.
2. Description of Related Art
The manufacture of semiconductor circuitry is a complicated process. It becomes even more complicated when monolithic microwave circuitry including one or more passive components is to be included in an MMIC. For example, each capacitor requires multilevel conductive plates, each resistor requires a layer of material having a predetermined conductivity and predetermined dimensions, and each inductor requires a high-Q metallic conductor. As used in this application, the term "conductive" is to be interpreted as including both higher conductivity materials, such as metals, and lower conductivity materials, such as doped semiconductors.
Further, to minimize electrical losses at microwave frequencies, thick metallic conductors should be used for making electrical connections to the passive components and for the inductor windings. As used in this application, the term "thick", as applied to a metallic conductor layer, is to be interpreted as meaning a layer thickness of at least two times the skin depth of the metallic conductor at the highest operational microwave frequency of signals carried by the conductor. conductor.
Known methods for forming conductive members in integrated circuits are overly complicated or are not capable of producing integrated circuits which are ideally suited for operation at microwave frequencies. For example, U.S. Pat. No. 4,789,648 discloses an apparently-simple process for producing multilevel metal/insulator films on a substrate and for forming patterned conductive lines simultaneously with connecting stud lines. However, a metal etch-stop layer utilized in the process is difficult to completely remove after the etching step is performed. This effectively prevents use of the metal etch-stop layer in areas where subsequently-deposited conductive layers are not to be electrically connected.